Bug#619719: autoconf2.64: ftbfs with dash from experimental (AC_PROG_GNU_M4 relies on echo preserving backslashes)

[Jonathan Nieder <jrnieder@gmail.com>]

Source: autoconf2.64
Version: 2.64-3
Severity: important
Justification: ftbfs with dash from experimental
Tags: upstream

Hi,

Trying to build autoconf2.64 with dash 0.5.6.1-1~exp2 as /bin/sh, I
get

	checking for GNU M4 that supports accurate traces... configure: error: no acceptable m4 could be found in $PATH.
	GNU M4 1.4.6 or later is required; 1.4.13 is recommended
	make: *** [configure-stamp] Error 1

This is because configure does

	ac_snippet=change'quote(<,>)in''dir(<if''def>,mac,bug)'
	ac_snippet=${ac_snippet}pat'subst(a,\(b\)\|\(a\),\1)d'nl
	test -z "`$ac_path_M4 -F conftest.m4f </dev/null 2>&1`" \
	&& test -z "`echo $ac_snippet | $ac_path_M4 --trace=mac 2>&1`" \
	&& test -f conftest.m4f \
	&& ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:

and expects bash's behavior (backslashes preserved rather than being
used for escape sequences) which is not portable.

Suggested fix: patch m4/m4.m4 to use $as_echo.  Or set CONFIG_SHELL
in debian/rules.

Thanks for keeping the toolchain working well.
Jonathan